The new pulse technique developed in our laboratory will be used to characterize the contractile properties of the left ventricle under a broadened range of conditions. These include the effect of preload and inotropic drugs in the beating non-pumping ventricle. As the next step the characterization will be generalized to the isolated and the in situ ejecting ventricle. In conjunction with our earlier characterization of the systemic arterial system, the ventricular characterization will be used to analyze, theoretically and experimentally, for the first time, the interaction between the events in the ventricle and the arterial system. This will allow specification of the conditions that unload the ventricle and determination to what extent such unloading takes place. Finally, the project permits the logical derivation of an improved index for cardiac 'contractility' which explicitly expresses cardiac performance for the given state.